Edit:
After some answers, an override of the event handling using jQuery is very acceptable. My issue is how to call the original onClick function with it's original prameters, and without knowing the function name.

You should change the generated HTML to not use inline javascript, and use addEventListener instead.

If you can not in any way change the HTML, you could get the onclick attributes, the functions and arguments used, and "convert" it to unobtrusive javascript instead by removing the onclick handlers, and using event listeners.

That gives us an array of all and any global methods called by the onclick attribute, and the arguments passed, so we can replicate it.

Then we'd just remove all the inline javascript handlers

$('button').removeAttr('onclick')

and attach our own handlers

$('button').on('click', function() {...}

Inside those handlers we'd get the stored original function calls and their arguments, and call them.
As we know any function called by inline javascript are global, we can call them with window[functionName].apply(this-value, argumentsArray), so